1. Field of the Invention
The present invention relates to a photogravure press and a method for manufacturing a multilayer ceramic electronic component performed with the photogravure press, and more particularly, to a technique for enhancing the smoothness of a paste film formed by gravure printing.
2. Description of the Related Art
In order to manufacture a multilayer ceramic electronic component, such as a multilayer ceramic capacitor, for example, a step of forming a conductive paste film defining an internal electrode on a ceramic green sheet is performed. The internal electrode must have high patterning accuracy. As a technique that satisfies this requirement, gravure printing has been used (for example, see Patent Document 1).
Japanese Unexamined Patent Application Publication No. 9-76459 (Patent Document 1) discloses that, of a plurality of cells provided in each print area provided on a peripheral surface of a gravure roll on which printing paste is applied, some cells provided in an outer peripheral portion of the print area have an open area that is smaller than that of the other cells provided in a center portion of the print area and the cells in the outer peripheral portion have a smaller depth than that of the cells in the center portion in order to ensure a uniform thickness of an outer peripheral portion of a paste film formed by gravure printing.
However, since the cells provided in the print area are independent from each other in Patent Document 1, the ratio of the sum of the areas of the cells to the total area of the print area is relatively low, and printing paste does not flow between the adjacent cells during printing. Therefore, this technique is unsuitable particularly for printing for forming a paste film having a relatively large area, and causes uneven printing.
As a technique that overcomes the above-described problems, walls that define a plurality of cells provided in a print area are provided and arranged so as to extend at an angle with respect to the printing direction, and cuts are provided in the walls that define the cells so that the adjacent cells communicate with each other, although this is not intended to be applied to the field of electronic components (for example, see Japanese Examined Utility Model Registration Application Publication No. 5-41015 (Patent Document 2)).
According to the above-described technique disclosed in Patent Document 2, the ratio of the area of a region in which printing paste is received (that is, cells and cuts) to the total area of the print area is increased, and the printing paste flows through the cuts.
However, in the technique disclosed in Patent Document 2, it is essential that a gap of each cut is less than a width of a wall. Therefore, when printing paste having a relatively high viscosity, such as conductive paste, is used, flow of the printing paste between the adjacent cells is limited. As a result, traces of the cells remain in a printed paste film, and a smooth paste film cannot be formed.
Further, in the technique disclosed in Patent Document 2, the walls that define a plurality of cells provided in the print area are arranged so as to extend at an angle relative to the printing direction. Therefore, when a printing sheet is separated from the gravure roll, so-called stringiness of the printing paste occurs at an angle to the printing direction, that is, to the moving direction of the peripheral surface of the gravure roll, and local irregularities are produced in a peripheral portion of the printed paste film.
While the above-described stringiness occurs in a direction at an angle to the printing direction, the direction is not fixed. Therefore, strings of the printing paste at a plurality of locations flow together and are combined. This leads to variations in the thickness of the paste film.